LRTKで変わる3次元測量：高精度なのに低コスト、専門オペレーターも不要

In recent years, advances in surveying technology have made advanced 3D surveying—once handled only by specialist surveyors—more accessible. Technologies that convert terrain and structures into three-dimensional data using drones and laser scanners have emerged and attracted attention in construction and infrastructure fields. On the other hand, persistent concerns such as “expensive equipment and skilled operators are required” and “difficult to master” have left some sites reluctant to adopt the latest technologies.

Enter LRTK, a new approach that combines smartphones with satellite positioning technology. LRTK is an innovative surveying tool that enables centimeter-level high-precision positioning (half-inch accuracy) simply by attaching a pocket-sized RTK-GNSS receiver to a smartphone. It is easy for anyone to use without specialist operators, and its combination of high accuracy and low cost is expected to dramatically lower the barriers to 3D surveying. This article explains the basics of 3D surveying, compares it with conventional methods, and introduces the new surveying approach using LRTK that has emerged amid the digital transformation (DX) trend. With examples of use in construction sites, infrastructure maintenance, and urban planning, we present how LRTK is reshaping surveying and its practicality and benefits.

3次元測量とは

3D surveying, as the name implies, is a surveying method that measures an object in three directions—length, width, and height—and acquires it as volumetric data. By recording the shape of terrain, buildings, and structures as three-dimensional coordinates (X, Y, Z), it can accurately reproduce complex shapes that are difficult to grasp with conventional two-dimensional drawings. For example, point cloud data (collections of numerous measurement points) obtained by scanning objects with lasers or cameras enable digital visualization of rock surface irregularities and building details. Much 3D surveying is performed as a non-contact method, measuring from a distance without physically touching the object, making it suitable for surveying steep terrain that is difficult to enter or large structures. In recent years, initiatives such as *i-Construction* promoted by the Ministry of Land, Infrastructure, Transport and Tourism have supported adoption, and 3D surveying is becoming standard technology in the civil engineering and construction industries. There is growing demand for 3D data use across a wide range of areas, from on-site as-built management to design and construction planning, maintenance, and the construction of urban infrastructure digital twins.

従来の測量手法と課題

Conventional methods used to obtain 3D survey data include the following. Each has advantages, but also faces challenges in terms of cost, effort, and required expertise.

• Total station surveying: This method uses an optical distance-measuring instrument called a total station (TS) to measure angles and distances at multiple points one by one to calculate coordinates. It can achieve millimeter-level high precision and is highly reliable, but because observations are taken point by point, measuring wide areas of terrain requires very large amounts of time and labor. It is a traditional method that relies heavily on manual work and requires careful operation by skilled operators.

• Drone photogrammetry: Small unmanned aerial vehicles (drones) equipped with cameras take many aerial photographs of the ground, and software reconstructs the three-dimensional shape. UAV photogrammetry revolutionized surveying by enabling short-time aerial surveys of inaccessible areas such as forests and large reclaimed land, and its adoption has increased recently. However, drone flights require compliance with aviation laws and piloting skills, and operations are restricted in urban areas or bad weather. The process of generating models from photos is time-consuming, and improving accuracy requires extra effort such as installing ground control points (GCPs).

• Terrestrial laser scanner surveying: A ground-mounted laser measurement instrument (3D laser scanner) is rotated to densely scan surrounding structures and terrain. It can capture hundreds of thousands to millions of points as point clouds, producing extremely detailed 3D data. Accuracy is high, making it effective for as-built management and displacement measurements of structures, but the equipment is large and expensive (millions to tens of millions of yen), and transport and setup are laborious. Raw data include noise, so specialist tasks such as noise removal and integration of multiple scan datasets using dedicated software are essential.

• GNSS surveying (RTK): This method uses satellite positioning systems such as GPS to determine position coordinates on Earth. In particular, RTK (real-time kinematic) corrects errors through simultaneous observations of a base station and a rover, allowing real-time positioning with centimeter-level accuracy. Traditionally, high-precision GNSS surveying required expensive dedicated receivers and communication devices, and it was common to outsource to surveying companies or have skilled operators handle the equipment. Moreover, the output is limited to individual point coordinates, so capturing the shape of surfaces or volumes requires numerous point measurements or combination with other methods.

As described above, conventional 3D surveying methods each have pros and cons. Precise surveying has typically required expensive dedicated equipment and specialist skills, making adoption difficult for site technicians. Many sites faced dilemmas such as “we can’t measure the locations we need right away” and “data processing and sharing take too long.”

測量分野におけるDXの進展

In recent years, DX (digital transformation) has been a rallying cry across the construction industry, and digital technology is making inroads into surveying. Initiatives like *i-Construction* and “smart construction” represent efforts to dramatically improve productivity using ICT, and these efforts are progressing rapidly. In surveying, the movement to digitize tasks that previously relied on tapes, levels, and total stations—manual work done by people—is accelerating.

Advancing on-site DX brings various benefits to surveying. Digitizing tasks that rely on human labor can help alleviate labor shortages and reduce human error, and results previously recorded on paper drawings or ledgers can be shared instantly in the cloud. For example, measurement results that used to be recorded by hand on site and then redrawn into drawings or used to prepare reports back at the office can now be automatically recorded and calculated as electronic data at the time of measurement, with photos saved together with location information, greatly reducing the burden of record-keeping. On-site data can be shared in real time with supervisors or clients in the office, allowing as-built conditions to be checked and instructions given remotely. Smooth data linkage enables on-the-spot corrective instructions when problems arise, accelerating the PDCA cycle of construction management and leading to earlier detection and correction of quality issues. In this way, the use of digital technology is transforming surveying itself and contributing to improved productivity and quality across the site.

LRTKを用いた測量手法の特徴

LRTK is a smartphone-mounted high-precision positioning system developed by a startup originating from Tokyo Institute of Technology. By attaching a small device weighing about 125 g and about 13 mm (0.51 in) thick to a commercially available iPhone or iPad with a single touch and launching a dedicated app, the smartphone itself becomes a centimeter-level surveying instrument. No complex setup is required; the current position is displayed in real time on the smartphone screen, and survey points can be recorded or plotted on maps and drawings on the spot while viewing your position. It is revolutionary in that it enables high-precision surveying, which was previously left to specialized equipment and skilled operators, to be used easily by anyone on site.

Main features of LRTK surveying:

• Centimeter-level high accuracy (half-inch accuracy): Using GNSS real-time correction technology (RTK), positions can be measured within an error range of several centimeters. Ordinary smartphone GPS has errors of several meters, but LRTK dramatically improves positioning accuracy by receiving correction information from a base station and performing calculations on the smartphone. The accuracy is sufficient to meet advanced civil engineering and surveying needs such as as-built management and checks against design lines.

• Easy operation without specialist knowledge: The smartphone app features a simple UI that allows survey point recording and photo capture by following on-screen prompts and pressing buttons. Even non-surveyors such as site supervisors and inspection staff can operate it intuitively, and guidance features help prevent measurement mistakes. For example, when a photo is taken, latitude, longitude, and orientation are automatically recorded and saved and shared together with notes. There is no need to operate multiple devices or record things by hand—anyone can perform “push-button surveying.”

• Real-time positioning and immediate sharing: With LRTK, measured data are not only recorded on the smartphone on site but can be uploaded to the cloud LRTK Cloud with one tap via mobile or satellite communication. managers in the office can instantly view measurement results in a web browser and download CSV or drawing data. This significantly shortens the time from measurement to reporting and smooths information sharing with remote locations. Even in areas without cellular coverage, LRTK supports the centimeter-level augmentation service (CLAS) provided by Japan’s quasi-zenith satellite *Michibiki*, allowing high-precision positioning to continue without the Internet for reliable operation.

• Compact, lightweight, and highly mobile: The LRTK device integrates with a smartphone and is pocket-sized, so workers can carry it at all times and measure whenever needed. Unlike conventional equipment, there is no need to transport heavy machinery or set up tripods; one person can walk the site and take measurements. For example, attaching LRTK to a helmet and patrolling a site makes it possible to perform continuous positioning while moving hands-free, enabling easy acquisition of wide-area terrain data.

• All-in-one multifunctionality: LRTK is not just a positioning device; it provides a variety of measurement functions required on site using only a smartphone. In addition to point coordinate measurement, it can perform continuous positioning at fixed intervals to record longitudinal and cross-sectional ground profiles, overlay design models on the real scene with AR (augmented reality) for verification, and guide stakeout (layout) operations. Combined with the iPhone’s LiDAR scanner, it can perform high-density 3D measurements by scanning the surrounding environment as a point cloud while assigning global coordinates to all points. Tasks that previously required dedicated surveying instruments or expensive 3D scanners can now be completed with just LRTK and a smartphone, greatly consolidating and simplifying on-site equipment.

• Low-cost introduction: LRTK is also attractive because its introduction cost is far lower than that of traditional surveying equipment. Since you can use your own smartphone, the only requirements are a small GNSS receiver (the LRTK device) and software subscription fees. High-precision surveying can be started from the scale of several hundred thousand yen, without purchasing laser scanners or dedicated instruments costing millions, making one-device-per-person deployment realistic. This resolves situations where limited equipment prevented timely measurement and makes it easier to establish an environment that allows immediate measurement when needed.

LRTKの実際の活用シーン

建設現場での活用

On construction sites, LRTK dramatically improves the efficiency of as-built measurement and layout (staking out) tasks. For example, in roadworks, height checks after concrete placement and slope measurements previously required summons of a surveying team. After LRTK adoption, site supervisors and workers can measure pavement height on the spot and immediately confirm whether it meets design specifications. Measurement results are shared via the cloud with office engineers, enabling real-time remote checks and immediate instructions if problems are found. Eliminating waiting time for surveys and enabling immediate self-measurement during construction breaks greatly increases productivity.

LRTK is also useful for structure positioning (layout/staking out). Because design coordinates on drawings can be confirmed on site, stake driving and foundation placement tasks that once required two people with a total station can be performed accurately by a single person. In earthworks, the volumes of finished embankments and excavations can be instantly calculated from point cloud data measured by LRTK. For rebar inspections and buried object confirmations, simply taking a photo with an LRTK-equipped smartphone leaves a record with date, latitude, and longitude, greatly improving the reliability of evidence compared with conventional photos that include a blackboard. Improved accuracy in site quality control and progress management, together with automated report generation from survey results, reduce the burden on site supervisors and speed up construction.

インフラ維持管理での活用

LRTK is also useful for maintenance of existing infrastructure such as bridges, tunnels, and roads. During routine inspections, inspectors can take photos of structure surfaces with an LRTK-equipped smartphone, automatically and accurately recording the location of cracks and abnormalities with latitude and longitude. What used to be manually marked on inspection drawings can now be digitally recorded with one tap, eliminating later cross-checking with drawings and simplifying long-term comparisons. LRTK is also effective for measurements at heights or in hazardous locations. Using LRTK’s target positioning function, coordinates of unreachable points such as the upper parts of bridge piers or a single spot on a steep slope can be measured precisely from a distance through a camera. This non-contact capability allows location identification without erecting scaffolding or climbing to heights, reducing risk and improving inspection safety.

LRTK also aids in damage assessment following natural disasters. In sites where roads have collapsed due to earthquakes or heavy rain, pocket-sized LRTK can be mounted on a helmet to allow pedestrian surveys. Even in areas where mobile communications are cut off, satellite augmentation signals enable standalone positioning, so accurate coordinates and extents of damaged areas can be recorded on site and quickly shared later via the cloud. The ability for on-site personnel to conduct initial surveys immediately after a disaster without waiting for large survey vehicles or personnel is a major advantage. This flexibility makes LRTK a promising new tool for infrastructure maintenance and disaster response.

都市計画での活用

LRTK is also effective in urban spatial data maintenance and town planning. In urban areas where drone flights are restricted and surveying is difficult, LRTK allows walking surveys to capture street and building layouts and reflect them in 3D models and maps. For example, city office staff using LRTK to巡回測定 roadsigns, utility poles, and block boundary locations can efficiently build detailed urban infrastructure GIS data. Surveys that previously required contractors can now be carried out frequently in-house, keeping current-condition data for urban planning consistently up to date. LRTK surveying can also be applied to 3D recording of historic buildings and cultural properties; easily creating high-precision digital archives contributes to future urban development and the preservation and utilization of tourism resources. In addition, when constructing a city’s digital twin as part of smart city initiatives, real-time urban data obtained with LRTK plays an important role. These uses in urban planning support more accurate and flexible decision-making for city development.

LRTKがもたらす新しい測量の姿

The advent of LRTK is beginning to fundamentally change the nature of surveying. High-precision surveying can now be practiced by “anyone, anywhere, anytime,” and surveying is being democratized from a task for a few specialists into a basic on-site tool. This smooths construction processes that used to be stalled while waiting for surveys, enabling flow-based work where measurements and confirmations are made immediately when needed and work progresses to the next step. Real-time information sharing between the site and headquarters or clients enables integrated team construction across geographic distances. As data accumulate, developments toward data-driven management—such as trend analysis of as-built conditions and advanced quality control—are expected.

Moreover, if one LRTK device per person becomes widespread, the ability to measure whenever desired will become the norm, and on-site decisions will always be based on the latest data. This is also effective for safety management, allowing quick response to subtle ground subsidence or structural displacements. Amid concerns about a shortage of experienced surveyors, allowing site staff to perform surveying helps bridge gaps in skill transfer and move toward less person-dependent systems. The combination of ease-of-use and high accuracy provided by LRTK aligns with the goals of *i-Construction* promoted by the Ministry of Land, Infrastructure, Transport and Tourism and can be seen as a next-generation solution underpinning DX across the construction industry. The new surveying style that LRTK is bringing about is expected to spread to more sites and bring about a revolution in both work efficiency and quality.

まとめ

LRTK, which enables high-precision yet easy-to-use surveying, is truly a trump card for lowering the barriers to on-site surveying. As described above, its practicality as a simple surveying tool that anyone can use is being increasingly proven, and the efficiency and labor-saving benefits it brings are considerable. Freeing sites from cumbersome surveying work and shifting to construction management based on real-time, accurate data is a major revolution for the field. By utilizing LRTK, teams can pursue the balance of productivity and quality with flexible thinking unconstrained by conventional norms. Embracing the latest technologies and starting DX through simple surveying can be the first step to bringing new value and competitiveness to your site. Now is the time to move beyond traditional methods and experience the practical benefits LRTK can bring to the field.